The present invention relates to a transfer sheet suitable for the formation, with high precision and ease, of electrode patterns, dielectric layers, barrier layers, etc. for use with plasma display panels (PDPs), field emission displays (FEDs), liquid crystal displays (LCDs), fluorescent displays, hybrid integrated circuits, etc.
For fine patterns such as electrodes, dielectric layers, barrier layers, etc. for use with PDPs, it is now required that they be fabricated at low fabrication costs while thickness accuracy and pattern accuracy are maintained at high levels.
So far, patterns for use with PDPs have been provided by forming a patterning paste having desired properties into a given pattern by a printing process such as screen or offset printing, followed by drying, and firing. This printing process involves simple steps, and so is expected to lead to production cost reductions. However, problems with the screen printing process are that the elongation of a mesh material forming a screen printing plate places some limitation on printing accuracy, and that the edge accuracy of the resultant pattern becomes low due to the occurrence of meshes in the pattern or the spreading of the pattern. A problem with the offset printing process is, on the other hand, that thickness accuracy and pattern accuracy decrease with increasing printing cycles because some patterning paste is not perfectly transferred to a substrate and so remains on a blanket. It is consequently required to make frequent blanket replacements, thereby preventing the paste from remaining on the blanket and maintaining the accuracy of the pattern upon forming. The operation to this end is, however, very troublesome.
A given thick-film pattern having a high aspect ratio, e.g., a PDP barrier pattern, has so far been formed by a screen printing process. With the screen printing process, the limitation of film thickness formed in one single cycle is of the order of a few tens μm. In other words, printing and drying cycles should be repeated many times, generally 10 or more times. A coating film formed by the screen printing process is generally of a convex shape in section or is bulging out. Consequently, when a multiplicity of printing cycles are carried out as mentioned above, coating solution sags are built up at the periphery of the pattern, and so make the pattern have a spreading bottom.
It has recently been proposed to form a barrier layer using a transfer sheet comprising a glass paste provided on a base film (JP-A 8-273536). This process makes use of the transfer sheet having a glass paste layer, and is advantageous in that the process of fabricating barriers for PDP panels can be simplified. However, problems arise in connection with the trapping of air bubbles by transfer, and the releasability of the glass paste layer from the base film. Especially when a fine electrode pattern or dielectric layer is formed by use of the transfer sheet, air bubbles, etc. are likely to pass into the transfer layer. Also, poor transfer causes breaks in the electrode pattern or pinholes in the dielectric layer.
In view of such problems as mentioned above, one object of the invention is to provide a transfer sheet which can be used to form, with great accuracy, fine patterns such as electrodes, resistors, e.g., dielectric layers, barriers, etc. for use image displays such as PDPs and LCDs, thermal heads, integrated circuits, etc.
Another object of the invention is to provide a transfer sheet which can be used to form, with great accuracy, primer layers, dielectric layers on front and back panels, photosensitive black matrix layers, and photosensitive rib layers for use with PDPs in particular.
Yet another object of the invention is to provide a transfer sheet which makes it possible to form a high-definition electrode pattern.